This invention relates generally to a manually actuated pump sprayer adapted for dispensing liquid from a container in both upright and inverted modes. More particularly, the pump sprayer has a container vent for equalizing the pressures within and outside the container when the pump is in operation to thereby prevent hydraulic lock of the pump piston, the vent being in the form of a spiral vent groove.
In the prior art pump sprayers of the type shown in the U.S. Pat. Nos. 4,051,983, 4,154,374 and 4,986,453 the closure cap is directly or indirectly coupled to the pump cylinder at its upper end for supporting the pump body within the interior of the container to which the pump body is mounted. A vent path is defined from inside the container via the top of the pump cylinder and between the closure cap and the piston stem to the ambient for venting the container during the piston downstroke and upstroke movements for replacing the liquid dispensed from the container with air to prevent container collapse during pumping and hydraulic piston lock. A depending collar on the closure cap is seated against an upper end of the pump piston at the end of the piston upstroke movement for sealing the vent path closed from the atmosphere to thereby avoid leakage through the vent path during shipping and storage of the pump assembly.
These sprayers are not readily adapted for operation in an inverted or steeply slanted position, even with the provision of an inverted adaptor of the type disclosed in U.S. Pat. Nos. 4,277,001 or 4,775,079, since the container vent which opens during the upstroke and downstroke of movements of the piston during pumping allows for leakage of liquid product therethrough in that the vent path is not designed to restrict the passage of liquid nor is the vent path designed to control the rate of venting relative to product displacement during spraying.
U.S. Pat. No. 4,277,001 discloses an upright/inverted sprayer having spaced vent ports located in the pump cylinder wall controlled by upper and lower skirts on the piston. However, leakage of product through the open container vent port or ports during pumping is not positively avoided since the valved vent port arrangement is incapable of controlling the rate of venting in relation to the product being dispensed during pumping. Besides, an additional vent skirt on the piston is required which adds to the cost and complexity of the pump assembly.
U.S. Pat. No. 4,775,079 discloses an upright/inverted pump sprayer having an elongated vertical vent path to avoid the ingestion of any air bubbles into the pump chamber during an inverted spray mode. However, such an elongated vent path requires a special tube or modified design of the pump assembly which only adds to the cost and complexity of the unit. Besides, the rate of venting is not readily controlled by such a design so that leakage through the open vent path could occur.